Leadscrew-adjusted potentiometer slider

ABSTRACT

A special contact-carrier or slider for leadscrew-adjusted potentiometers, consisting of an insulative block having a longitudinal screw-receiving groove and a transverse slot in which is fitted a resilient screw-engaging yoke which facilitates assembly of the contact-carrier and potentiometer and permits overdrive of the actuating screw without damaging effect on the potentiometer.

United States Patent Joseph R. DeRouen Inventors Banning; William 11. King, Riverside; Raymond T. Dion, Rialto, all of, Calif. Appl. No 821,415 Filed May 2, 1969 Patented June 1, 1971 Assignee Bourns, Inc.

LEADSCREW-ADJUSTED POTENTIOMETER SLIDER 3 Claims, 4 Drawing Figs. US. Cl 338/180, 338/202 Int. Cl 1101c 9/02, l-lOlc 5/02 Field ofSearch 338/118,

Primary Examiner-Lewis H. Myers Assistant Examiner-Gerald P. Tolin Attorney-Fritz B. Peterson ABSTRACT: A special contact-carrier or slider for leadscrewadjusted otentiometers, consisting of an insulative block having a longitudinal screw-receiving groove and a transverse slot in which is fitted a resilient screw-engaging yoke which facilitates assembly of the contact-carrier and potentiometer and permits overdrive of the actuating screw without damaging effect on the potentiometer.

A aw pix; r /o SUMMARY OF THE INVENTION In the prior art leadscrew-adjusted potentiometers, a wide variety of means have been disclosed for converting rotational motion of the leadscrew into translational motion of a contact carrier whereby to translate the contact or contacts to a desired location along the resistance element. Included among the prior art means are resilient blocks of elastomer with arms or sections which embrace the leadscrew and, either with or without aid of complementary threads, effectively convert the rotational motion of the screw to linear motion of the block and contact. Such devices are illustrated in U.S. Pat. Nos. 2,873,337; 3,412,362 and 2,898,569. Another type of prior art slider construction utilized resilient metallic devices which rendered the leadscrew electrically active and which generally required means for insulating a portion of the leadscrew. Such sliders are illustrated in U.S. Pat. Nos. 2,873,338; 2,895,116 and 2,882,375. A third type of prior art slider construction employed an insulative block or body to which the contact is attached, and characterized by the block further carrying a wire, clip or like means which engages the leadscrew thread and converts rotational motion of the screw to linear motion which is transmitted to the block and contact. This latter type of construction is illustrated in U.S. Pat. Nos. 3,124,779; 3,124,780; 2,946,975 and 2,945,199. The present invention, employing an insulative slider body and a resilient metal yoke to engage the thread of the leadscrew, is most nearly associated with this third type of slider construction, but presents considerable and important improvements upon the prior art devices in permitting the ready assembly and disassembly of the slider structure, in reducing the cost of manufacture, in permitting considerable reduction in size of the slider structure, and in durability of the potentiometer in which the novel slider is used.

Essentially the slider structure comprises a cast or molded blocklike body having a longitudinal shaped groove dimensioned to slidably accommodate a portion of the threaded middle part of the leadscrew and further having a transverse yoke-receiving slot which transversely intersects the groove and which receives a resilient wire yoke comprised in the structure. The yoke is devised with a middle portion adapted to fit in the bottom of the transverse slot below the leadscrew, and first and second opposed upstanding limbs which are devised to resiliently clasp or embrace the leadscrew. The block or body of the slider comprises means for holding the potentiometer contact, and preferably, but not necessarily, is of durable electrically insulative material such as polytetrafluoroethylene or other synthetic resin. Thus, in cident to rotation of the leadscrew around its longitudinal axis, the resilient limbs of the yoke are engaged in a groove of the leadscrew and are forced to translate along the screw, being prohibited from rotation with the screw by means which prohibit the block from such rotation. The yoke is held captive in the slot in the slider body by the leadscrew, and hence transmits its translatory motion directly to the block and thereby to the contact. The limbs of the yoke are integral with the middle portion and are shaped with outwardly curved ends whereby by force applied to the middle portion transversely of the leadscrew the yoke is readily brought into engagement with the thread of the screw. Such force may be applied directly, or via the block or body in which case the body is concurrently brought into proper engagement with and juxtaposition to, the leadscrew. Since the yoke is merely pressed straight into the slot in the slider body without deformation, it is evident that it is easily assembled to the block. And since the block may be merely pressed onto the leadscrew with the yoke between the block and leadscrew, assembly and disassembly are very easily and quickly accomplished. The yoke, a length of resilient wire, is inexpensive as to both material and manufacture. Thus, by virtue of the inexpensive character of both the block or body and the yoke, and the extremely simple and rapid assembly, the cost of a potentiometer is markedly reduced.

2 DESCRIPTION OF THE DRAWING FIG. I is a longitudinal sectional view of a leadscrew-adjusted potentiometer incorporating the present invention, and illustrating the novel slider in operative position relative to the resistance element and leadscrew;

FIG. 2 is a transverse sectional view of the potentiometer depicted in section in FIG. 1, illustrating the relationship of housing members, leadscrew, slider, terminal members, element, and collector; I

DIG. 3 is a view of a resilient yoke component of the leadscrew-driven slider of the invention; and

FIG. 4 is a pictorial representation of the block component of the slider of the invention.

DESCRIPTION OF THE EXEMPLARY PREFERRED EMBODIMENT OF THE INVENTION It will be understood that the improved slider of the present invention can be adapted for use in a wide variety of forms of leadscrew-adjusted potentiometers; and that solely for purposes of facilitating explanation and illustrating the general environment of the invention, the slider has been shown as incorporated in an otherwise conventional cermet-element leadscrew-adjusted potentiometer whose other parts and components are described only to the extent necessary for a full understanding of the invention.

The potentiometer, denoted generally by number 10, comprises a case or housing formed principally ofa base 12 and a cover 14. Both principal housing components are conventionally formed of synthetic resin or other polymeric material, generally with an inert filler included. The cover 14 is of elongate boxlike form, having ends and sides as shown in FIGS. 1 and 2. At one end the cover is formed with a bore 14b in which is journaled the head end of a conventional leadscrew 16. The opposite end 16a of screw 16 is confined in a slotlike recess between two opposed abutments, such as 14s, formed at that end of the cover.

The base 12 is provided with molded-in terminal members T1, T2 and T3, and has secured on the inner face thereof a ceramic substrate 18 on which is disposed a thin filmlike resistive element 18e and a thin return conductor 180. As indicated, the conductor 18c is connected to terminal T3, and the ends of element I8e are connected to respective terminals TI and T2. In the operation of assembling the potentiometer 10 the cover 12 is disposed upsidedown, with the open face of the boxlike cover upward. The leadscrew 16, with its O-ring seal applied, is inserted through bore 14b and 16s seated in the groove between the confining abutments, and retainer R is pressed into complementary grooves in the screw and cover. Thereafter the novel slider structure of the present invention is dropped or pressed down in the cover into straddling relationship with the leadscrew. The slider structure, designated by number 20, comprises block 22 and yoke 24 and will presently be explained in detail. Following insertion of the slider with its attached contact, the base 12, inverted, is lowered onto the inverted cover, with a sealant preform 26 therebetween; and the sealant activated (as by heat) to secure the cover to the base. As is made evident in FIGS. 2 and 3, the slider body is dimensioned so that one or all of its parallel sides 22a, 22b and top surfaces 22! and 22a, engage complementary interior surfaces of the cover 14, whereby the body 22 is prevented from rotating with the leadscrew and is permitted to translate to and fro along the interior chamber formed by the potentiometer housing. As is also made evident by the drawings, during assembly of the base onto the cover, the substrate l8 enters the cover and stresses the limbs or tines of a resilient contact device C carried by the slider and which will presently be more fully explained.

Referring to the drawings and more particularly to FIGS. 3 and 4, the slider body 22 is shown to be a shaped blocklike member having parallel side faces 22a and 22b, and a transverse slot 225. The slot 22s is preferably not formed at right angles to the side faces 22a and 22b, but at a slight angle thereto so as to be complementary to the pitch of the thread of the leadscrew 16. That is, the slot is formed so that the portions thereof in the opposed limbs or risers of the body 22 are longitudinally displaced one-half of the pitch or lead of the thread of screw 16. Further, body 22 of the slider has means, here shown on the bottom surface thereof, for attachment of the contact C. For that purpose the body has a shallow lon gitudinal depression 22d adapted to receive the platelike portion of contact C, and a button 22x (FIG. 1) which is passed through a complementary opening in the contact and heatswaged or deformed to retain the contact to the body in a conventional manner illustrated, for example, in U.S. Pat. No. 2,873,337. The attachment of the contact to the body of the slider is not per se the present invention, and is here disclosed only by way of example in showing a complete potentiometer.

As is made evident in H08. 2 and 3, the yoke 24 is formed with a middle portion 240 adapted to fit in the bottom of the transverse slot 225 formed in the body 22, and with first and second upstanding limbs 24b and 24d integral with the middle portion and each adapted to yield outwardly away from the other under the influence of appropriately applied forces, and to resiliently return to relaxed condition following removal of the applied forces; Whereby to facilitate effective engagement of the yoke with the threaded portion of the leadscrew, and to improve the spring action and block-driving action of the yoke, each of the limbs 24b and 24d is reversely bent inwardly at its upper extremity, as clearly shown in FIG. 3. Thus there are formed upwardly divergent cam surfaces 24c and 24f which are effective to cam the limbs further apart incident to the yoke being pressed into engagement with the leadscrew as depicted in FIG. 2. The terminal ends of the yoke wire are curved downwardly and outwardly, whereby the sharp edges of the wire ends do not come into contact with the leadscrew and hence such edges cannot damage the screw thread.

When positioned on the leadscrew the curved innermost portions 24g and 24h of the yoke limbs enter into a groove of the leadscrew thread, between next-adjacent land convolutions of the thread, as indicated in FIG. 2. Thus positioned, the outer or riser portions of the yoke limbs are positioned in slot 22 of the slider body, in driving engagement with the latter. When the leadscrew is overdriven so that the slider body is brought into collision with the cover of the potentiometer housing at either end of the chamber, the limbs of the yoke yield to the cam action of the thread of the leadscrew, and alternately spread outwardly and spring back inwardly as excessive rotation of the screw is continued. The inward snapping of the limbs from the land to the groove of the thread of the screw produces an audible indication of the overdrive of the screw and of the fact that the slider and its contact have been driven to one extreme of its traverse. The yielding action of the yoke, sometimes referred to as ratcheting, results in avoidance of damaging of any of the parts of the potentiometer.

As may be conventional in potentiometers, the contact C is of metal or conductive alloy and has fingers which resiliently brush on the resistive element 18:: and the return conductor 18c, as is indicated in FIG. 2 Thus potential applied across the resistive element may be apportioned or divided with an ad justable fractional portion apparent between terminal T3 and either of terminals T1 and T2.

When the base 12 is assembled with the cover 14 of the potentiometer, force exerted by the spring contact C is transmitted to the leadscrew to hold end 16a thereof between the confining abutments such as 14s; and that means of retaining the inner end of the leadscrew in position may be aided or supplanted by a pedestal such as 12p (FIG. I) affixed to base 12 as indicated.

We claim:

1. A leadscrew-adjusted potentiometer in which a leadscrew having a thread comprising a land and a groove is supported for rotation about its longitudinal axis and presents an exposed threaded portion, and in which resistive means is disposed with a contact surface parallel to the leadscrew axis and disposed to be brushed by a contact device moved therealong,

the im roved combination with those parts comprising:

a bocklike slider body having a longitudinal groove in which a length of the leadscrew is received for relative translation of the body along the leadscrew, said body carrying thereon a contact device in brushing contact with the resistive means and said slider having a transverse slot therein generally intersecting said groove; and

a resilient wire yoke comprising first and second opposed limbs and a middle portion interconnecting said limbs and extending transversely across said body in said slot out of contact with the leadscrew, each of said limbs disposed in part in said slot and each having a portion spaced from the end thereof yieldingly engaging the thread of the leadscrew, whereby incident to rotation of the leadscrew said slider body is translated along the leadscrew without sharp metal edges engaging the leadscrew, by engagement of said yoke with said body and the leadscrew, and whereby the dimensions of said body are minimized and incident to overdrive of the leadscrew and arrestment of translation of said body said limbs are spread and ride out of a groove and over a land of the leadscrew to avoid damage to the potentiometer.

2. A leadscrew-adjusted potentiometer as defined in claim 1, the combination of slider body and wire yoke as therein defined, said wire yoke comprising in each of said first and second limbs an outer riser portion and a depending curved inner portion joined to the riser portion by a reverse bend, whereby said yoke may be readily pressed onto the leadscrew by application of force applied to the interconnecting portion thereof transversely of the leadscrew.

3. A leadscrew-adjusted potentiometer as defined in claim 2, said slider body having means for positioning and attachment thereto of said contact device. 

1. A leadscrew-adjusted potentiometer in which a leadscrew having a thread comprising a land and a groove is supported for rotation about its longitudinal axis and presents an exposed threaded portion, and in which resistive means is disposed with a contact surface parallel to the leadscrew axis and disposed to be brushed by a contact device moved therealong, the improved combination with those parts comprising: a blocklike slider body having a longitudinal groove in which a length of the leadscrew is received for relative translation of the body along the leadscrew, said body carrying thereon a contact device in brushing contact with the resistive means and said slider having a transverse slot therein generally intersecting said groove; and a resilient wire yoke comprising first and second opposed limbs and a middle portion interconnecting said limbs and extending transversely across said body in said slot out of contact with the leadscrew, each of said limbs disposed in part in said slot and each having a portion spaced from the end thereof yieldingly engaging the thread of the leadscrew, whereby incident to rotation of the leadscrew said slider body is translated along the leadscrew without sharp metal edges engaging the leadscrew, by engagement of said yoke with said body and the leadscrew, and whereby the dimensions of said body are minimized and incident to overdrive of the leadscrew and arrestment of translation of said body said limbs are spread and ride out of a groove and over a land of the leadscrew to avoid damage to the potentiometer.
 2. A leadscrew-adjusted potentiometer as defined in claim 1, the combination of slider body and wire yoke as therein defined, said wire yoke comprising in each of said first and second limbs an outer riser portion and a depending curved inner portion joined to the riser portion by a reverse bend, whereby said yoke may be readily pressed onto the leadscrew by application of force applied to the interconnecting portion thereof transversely of the leadscrew.
 3. A leadscrew-adjusted potentiometer as defined in claim 2, said slider body having means for positioning and attachment thereto of said contact device. 